Iron wheels roll over rail surfaces to drive a railroad vehicle, and the railroad vehicle is characterized by small running resistance compared to an automobile. Particularly, in a recent electric railroad vehicle, a main motor is operated as an electricity generator during braking to obtain braking force. At the same time, regenerative brake control is performed in which the electric energy generated by the main motor is returned to the trolley wire to reuse the electric energy as powering energy of other vehicles. The electric railroad vehicle with the regenerative brake can travel by about half the energy consumption compared to an electric railroad vehicle without the regenerative brake. It can be stated that this is an energy saving method utilizing a feature of the railroad vehicle with low running resistance.
Meanwhile, in a local railroad and the like with low transport density, a diesel railcar that does not require trolley wire, electric power substations, and the like realizes sophisticated passenger services with low cost.
However, the diesel railcar does not include means, such as trolley wire, for transferring energy to other vehicles, and there is no reuse of regenerative energy as in the electric railroad vehicle. Therefore, there is no choice but to depend on the development of a high-mileage engine to realize energy saving in the diesel railcar.
Consequently, a hybrid vehicle with a combination of an engine and an electricity storage apparatus is devised as one of the methods for promoting energy saving in the diesel railcar. The installation of the electricity storage apparatus allows the hybrid vehicle to temporarily absorb, in the electricity storage apparatus, regenerative energy generated during braking. Energy saving is realized by reusing the absorbed regenerative energy as part of energy necessary during powering.
In this way, compared to the conventional diesel railcar that directly transmits an engine output to the wheel and axle through a decelerator to obtain traction force of the vehicle, the hybrid vehicle drives an electricity generator by an engine output to convert the engine output to DC power and converts the DC power to AC power by an inverter apparatus to drive a motor to generate traction force. Meanwhile, during braking, the inverter apparatus converts the AC power generated by the motor to DC power, and the electricity storage apparatus connected to a DC power section is charged with the DC power. It can be stated from another viewpoint that the hybrid vehicle is a system in which an engine electricity generator that generates electric power and an electricity storage apparatus that absorbs regenerative electric power are added to a driving system for electric train.
A configuration and a control system of the hybrid vehicle are described in a railroad vehicle driving system of Patent Literature 1.
FIG. 7 shows a device configuration diagram of the railroad vehicle driving system shown in FIG. 1 of Patent Literature 1. The railroad vehicle driving system includes: a first railroad vehicle 101 including electricity generation means 110, an electric power conversion apparatus 120, a driving motor, and electric power storage means 150; and a second railroad vehicle 102 including the electric power conversion apparatus 120, the driving motor, and the electric power storage means 150, wherein the means are connected by electric power transmission means 140. The railroad vehicle driving system includes electric power management means 200 for controlling generated electric power of the electricity generation means 110 and controlling an amount of stored electricity of the electric power storage means 150, wherein the electric power storage means 150 stores electric power generated by the electricity generation means 110 and regenerative electric power, and the electric power conversion apparatus 120 uses the electricity generation means 110 and the electric power storage means 150 as power sources to drive the driving motor to drive the train.
In this way, in the railroad vehicle driving system shown in FIG. 1 of Patent Literature 1, the electric power is supplied from the first railroad vehicle including the electricity generation means 110 to the second railroad vehicle 102 including the electric power conversion apparatus 120, the driving motor, and the electric power storage means 150 that form a driving system similar to that of an electric train to realize operation of the vehicle.